The Influence of Synthesis Parameters on Structural and Magnetic Properties of Iron Oxide Nanomaterials

Abstract

Magnetic iron oxides have been used in biomedical applications, such as contrast agents for magnetic resonance imaging, carriers for controlled drug delivery and immunoassays, or magnetic hyperthermia for the past 40 years. Our aim is to investigate the effect of pressure and temperature on the structural, thermal, and magnetic properties of iron oxides prepared by hydrothermal synthesis at temperatures of 100–200 °C and pressures of 20–1000 bar. It has been found that pressure influences the type of iron oxide crystalline phase. Thus, the results obtained by Mössbauer characterization are in excellent agreement with X-ray diffraction and optical microscopy characterization, showing that, for lower pressure values (<100 bar), hematite is formed, while, at pressures >100 bar, the major crystalline phase is goethite. In addition, thermal analysis results are consistent with particle size analysis by X-ray diffraction, confirming the crystallization of the synthesized iron oxides. One order of magnitude higher magnetization has been obtained for sample synthesized at 1000 bar. The same sample provides after annealing treatment, the highest amount of good quality magnetite leading to a magnetization at saturation of 30 emu/g and a coercive field of 1000 Oe at 10 K and 450 Oe at 300 K, convenient for various applications.

Biocompatible Magnetic Colloidal Suspension Used as a Tool for Localized Hyperthermia in Human Breast Adenocarcinoma Cells: Physicochemical Analysis and Complex In Vitro Biological Profile

“…Hence, during the nanoparticle washing process, the hematite nanoparticles would be removed. Similar results were published by Cursaru and coworkers [ 59 ].…”

Synthesis and Use in Catalysis of Hematite Nanoparticles Obtained from a Polymer Supported Fe(III) Complex

“…[26] For example, hematite is the only iron oxide formed by hydrothermal methods at pressures less than 100 bar whereas at pressure higher than 100 bar goethite was formed. [27] Herein we describe the synthesis of crystalline nanohematite obtained by heating under air an amorphous polymer supported iron(III) complex and its use in the catalytic hydrogenation of nitroarenes.…”

One-Step Soft Chemical Synthesis of Magnetite Nanoparticles under Inert Gas Atmosphere. Magnetic Properties and In Vitro Study

“…Our previous studies have addressed the role of pressure and temperature on the formation of hematite (Fe 2 O 3 ) by the hydrothermal method [31,32].…”